.body {
    height: 100%;
    display: grid;
    grid-template-rows: auto 1fr;
    grid-template-areas: 
        "h"
        "m";
}

.header {
    grid-area: h;
    position: relative;
}

.use-name {
    position: absolute;
    top: 0;
    left: 100%;
    margin-left: -200px;
    height: 61px;
    line-height: 61px;
    display: block;
    font-size: 14px;
    padding-left: 24px;
    background: url(../../img/icon/use.svg) no-repeat 0 50% / 20px;
}

.main {
    grid-area: m;
}

.iframe {
    display: block;
    width: 100%;
    height: 100%;
}